Hyperkalaemia, cardiac arrhythmias, and cerebral lesions in high risk neonates.

The case notes of 20 infants with hyperkalaemia (defined as two successive serum potassium measurements of greater than 7.5 mmol/l) were reviewed. The incidence of hyperkalaemia was also looked at in an unselected population of 200 low birthweight infants. The mean gestational age of the 20 affected infants was 29 weeks and the mean birth weight 1235 g. The incidence of hyperkalemia in the cohort of 200 infants weighing less than 1500 g at birth was 3.5%. Hyperkalaemia was associated with a high incidence of cardiac arrhythmia (60%), impaired renal function (50%), and changes on cerebral ultrasonography (88%). Hyperkalaemia responds slowly to conventional treatment with dextrose, insulin, and exchange resins. There is a close temporal relation in some infants between hyperkalaemia and cardiac arrhythmias and periventricular leukomalacia, suggesting a causal association.